What is it?

You're looking at the future of the performance four-door. No kidding. Here’s a V6-powered luxury saloon that’s quicker to 60mph than a Tiptronic Porsche 911; quicker than any V8 rival, including the BMW 545i. Yet it’s more than 30 per cent more economical, and pumps out 80 per cent less CO2. Drum roll please: it’s the brand new Lexus GS450h. The ‘h’ is what’s key here.

It signifies the hybrid technology crammed into the engine bay. Unlike Toyota’s eco-weenie Prius, which uses electro-hybrid power to boost economy, Toyota’s Lexus division uses it for the unrelenting pursuit of power. The technology is mind-blowing, and would take up the rest of this week’s issue to fully explain, but it’s very similar to that used in the RX400h off-roader, though here using a 3.5-litre 292bhp V6 similar to the one in the forthcoming IS350.

This is coupled to not one, but two electric motors. MG1 – short for Motor Generator 1 – functions as a generator and starter. MG2 is the muscle part, delivering an additional 197bhp and 203lb ft. It’s enough to drive the GS around town on electric power alone. And as with all hybrids, there’s a stash of nickel metal-hydride batteries – 40 in the case of the GS – packed tightly between the rear seat and the boot (reducing boot space by 40 per cent).

But there’s more. Lots more. Because no one has so far developed a continuously variable transmission that works with rear-wheel drive, Toyota created the world’s first longitudinal, electronic CVT. Then, to provide even greater flexibility, Toyota engineers came up with a second planetary gearset that serves as a two-ratio torque multiplier. The 3.9:1 low gear helps rocket the car off the line, then the 1.9:1 high ratio kicks in to boost fuel economy and high-speed cruising refinement.

What's it like?

What does it go like? Smelly stuff off a shovel. Floor the throttle from rest and it lunges to 60mph in a mere 5.2 seconds, compared to 5.7sec for the V8-powered GS430. But even more impressive is its ability to flash past slower traffic. Mid-range acceleration is simply staggering – 30 to 50mph, for example, takes a mere 2.7 seconds.

The key here is that there’s none of the lag time you get waiting for a conventional automatic to downshift. With the Lexus the response is immediate. Of course, you’ll either love or loathe the CVT with its constant screaming revs – it sounds a bit like opening the throttle on an outboard motor. And V8 lovers will miss the deep, rumbly note of eight cylinders

But they certainly won’t miss a V8 when it comes time to fill up. Lexus reckons the 450h should be good for almost 36mpg, which is the kind of economy most 2.0-litre four-cylinder saloons average. For the 450h owner driving 15,000 miles a year, it should mean a saving of around 220 gallons of unleaded over comparable luxury cars. It’s super-clean too, producing CO2 emissions of just 186g/km.

Should I buy one?

Sadly, Lexus is making it hard to impress the neighbours with its latest wondercar. Apart from a discreet ‘hybrid’ badge mounted on the sills beneath the rear doors, and a chrome 450h badge on the bootlid, the car looks near-identical to the V8-powered GS430. Which is a pity, because you’ll have paid heavily for its stellar performance. Toyota GB is still working out pricing – the 450h goes on sale in late spring – but expect a price tag of around £48,000, which is only £1300 more than a V8-engined GS430, but hardly cheap

Of course, if all this isn’t enough, wait for the Lexus’s upcoming über flagship, the hybrid version of the all-new LS – the LS600h. It’s due in a year’s time and promises 0-60mph sprinting in under five seconds. As we said, the future starts here.